N00B to rc in general... Need advice on battery and motor possibilities...

[LazyDog]

I started with a +/-700mm deep-V hull ARTR boat... The original motor it had in it had a rating in the mid 2000kv range rated at 3s 4500mah and up. I ran a 3s 5000mah battery in it and burned out the motor (only) replaced it with a couple of higher kv'd motors and a couple in the lower KV range and cooked them to... By the suggestion of some (rc boat) guys at the lake I changed out cooling tube size and still managed to cook those motors, could it be that my 432 stock prop is to big? Anyone have any thoughts?

Thanks! =)

[LazyDog]

I read somewhere that any motor rated over 2000/2200kv is not for rc boats. Is this true?

I'm just trying to get some validity to it because if everything on the internet were true, then I'm a FRENCH MODEL!!! LOL

[Fluid]

Welcome LD! Motor Kv suitability depends on the voltage run through the motor. On 2S a 2200 Kv motor is pretty slow in most boats, but on 8S it is 'way too high. Without more information about your ARTR boat it is difficult to guess the problem. Stock ARTR motors are not always the best choices - why do the makers to that! If the prop is running submerged rather than surfacing then the prop may be too large. What are the dimensions of the motor - length and diameter? How long do you run the boat? This could be the problem as heat is cumulative - the longer the boat runs the hotter it gets, get the motor too hot and ******! The extra run time you got from the larger 5000 mAh pack may have been the issue. We just need to know a lot more specifics about you r application before we can be much help. Pics are always a help.


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[LazyDog]

Thanks Fluid. Well the boat I purchased is the EXCEED Racing Electric Powered Snap-720-EP-ARTR

Specification:
Length: 720mm
Beam: 173mm
Height: 125mm
Weight: 1000g
Hull Type: Fiberglass Dee V
Motor: 2848-2636KV water-cooled brushless (now updated to a Tacon 2848-380L-22T 1800KV Brushless Motor with a 120A ESC - Haven't run this setup yet!)
Propeller: Carbon-reinforced plastic D36*P1.4 3-blade
Driveline: Flex drive
Hardware: CNC aluminum strut and rudders

[gsbuickman]

Welcome LD. As a general safety net you want to stay under 37,000 rpm's full throttle. To get your max rpm, you multiply the motor kv rating by your battery voltage. My mean machine is running a 2030kv aquacraft on 4s Rev-tec 30c 6000mah cells. They're pushing an Octura m455 pro. It works great & it eats up water in a hurry. I time my runs so they're 4-5 min max.

You can do some searching to see what others are doing for sucessful combonations in that hull. you can run 4s with your 1800kv alright, but i think you'll need to adjust your prop size a bit.

[LazyDog]

Thanks Fluid and gsbuickman. I think maybe that is the key, I've been running my boat in spurts of full throttle and cruising for longer runs than 4-5mins... oops! Maybe I should build another boat to be out on the water longer...

Thanks again! BTW with this size boat could I go bigger in prop size with the motor-esc combo I have now?

[AlanD]

[QUOTE=.....I've been running my boat in spurts of full throttle and cruising for longer runs than 4-5mins... oops!....[/QUOTE]

LazyDog that may be your biggest burnout culprit right there. Running wide open throttle places less heat burden on your ESC than cruising but the motor burnout is most likely due to being overpropped and long runs.

You may want to get yourself a laser thermometer and measure temps after 2 minutes of WOT and see where you're at on temps. I document my temps on batteries, ESC, and motor during and after every run and very soon its easy to see what's normal and out of place.

[iop65]

a 2848 is rather small for a boat this size
i don't think it you can prop up either with that stock motor ,maybe the tacon can,not sure

such a boat needs a 2860 ,a 3650-3660 and be run on 3s or 4s for a decent speed and amp drawn

a speedboat needs to be run 80-90% of the time full throttle !